This is a study comparing two study drugs, Filgrastim Hospira and Neupogen®. Neupogen® is approved by the US Food and Drug Administration (FDA) to treat low numbers of specific kinds of white blood cells (WBC) known as neutrophils. This type of white cell is important in fighting infections. A low neutrophil count is known as neutropenia. Both drugs work by increasing the number of neutrophils that are produced in the body.